Deep drawn panels are usually stamped out of extra deep draw quality steel that has excellent formability. Parts made of extra deep draw quality steel are substantially heavier than parts made of aluminum alloys or advanced high strength steel that have equivalent strength. The need to reduce the weight of vehicles to improve fuel economy necessitates development of new techniques for forming parts from lighter and stronger aluminum alloys or advanced high strength steel.
Drawing aluminum alloys or advanced high strength steel panels to form a central deep cavity with sharp corners is very problematic because the material from a flange area of the blank cannot easily be drawn into the central cavity due, in part, to the contour of the features on the sides of the panel. A typical example of such a panel would be a dash panel for a vehicle, a passenger compartment floor pan, or the like. One approach to providing a large panel having deep cavities out of aluminum alloys or advanced high strength steel is to subdivide the part and form the part in multiple pieces. However, this multi-part approach adds processing steps such as assembly and welding steps and may result in less accurate part shapes with added potential for tolerance stack-ups.
Drawing wide parts with deep draw areas in extra deep draw quality steel may be accomplished without causing the material to split. However, attempts to form the same part with lighter weight materials having higher strength/lower formability using existing stamping technologies on conventional presses resulted in excessive splits. In particular, forming a dash panel using less ductile blanks of BH280, DP500, HSLA350 or aluminum alloy AA5182 produced large splits.
There is a need for forming technology for drawing large panels having deep cavities out of aluminum alloys or advanced high strength steel to achieve potential weight savings. This disclosure is directed to achieving this objective and other objectives as summarized below.